Mammalian retina contains a variety of ganglion cell types which can show different morphologic forms, functional properties and central projections (reviewed in Rodieck, 1979; Stone et al., 1980 ad Lennie, 1981). The development factors which give rise to the differentiation of retinal ganglion cells into distinct types remain largely unknown. It is likely, however, that both intrinsic genetic mechanism and extrinsic influences of the cells environment contribute. The experiments in this application are designed to increase our understanding of the development of normal retinal ganglion cell structure, projections and function as well as the manner in which the properties and projections retinal ganglion cells affect the organization of central visual areas. The effects of neonatal damage to the visual pathways as well as the manner in which congenital visual system defects, as in albinism, affect the structure and function of the visual pathways should also be clarified. Experiment 1 consists of a number of studies designed to investigate the morphological development of the different classes of retinal ganglion cells and to determine the extent to which class specific interactions with neighboring neurons during development affect retinal ganglion cell structure. Experiment 2 consists of a number of studies designed to determine the extent to which the retinal distributions and central projections of the different classes of ganglion cells depend upon class specific, activity dependent axonal interactions in the LGNd and/or superior colliculus during development. Experiment 3 is designed to determine the changes in the functional properties of alpha and beta type retinal ganglion cells which result when their cell body sizes and dendritic field structures are altered experimentally. Experiment 4 is designed to determine the changes in the receptive field properties and topographic organization of neurons in the LGNd and visual cortex which result when the structures and central projections of retinal ganglion cells are altered experimentally. These studies will be carried out using standard techniques including horseradish peroxidase histochemistry, computerized morphometric analysis, extracellular single unit recordings and computer controlled visual stimulation.